In a related art, a battery pack structure in which a high-power cut-off switch (a breaker box 30) is mounted on an upper surface of a battery case (a battery box 28), in an electric vehicle that mounts in a lower position of a vehicle body floor a battery pack (battery modules A), has been known (see e.g. Patent Document 1).
Further, a battery pack structure in which a high-power cut-off switch (a switch unit 44) is provided with the high-power cut-off switch (the switch unit 44) arranged parallel to a battery module (a sub-module 24) in a vehicle width direction, in an electric vehicle that mounts in a trunk room (a luggage boot) a battery pack (a vehicle power supply unit 10), has been known (see e.g. Patent Document 2).
In the case of the battery pack structure disclosed in the Patent Document 1, however, since the high-power cut-off switch is mounted in an upper surface position of a battery module mounting area of the battery case, a height of the battery case becomes higher than a total height of the battery module and the high-power cut-off switch. Thus, in order to secure a necessary ground clearance from a road surface to a lower surface of the battery case, there is no other way than to raise the vehicle body floor to a position at which an interference with the upwardly-protruding high-power cut-off switch is avoided. As a consequence, when the battery pack disclosed in the Patent Document 1 is arranged in the lower position of the vehicle body floor, a vehicle body floor surface is high, and a vehicle body floor upper space such as a vehicle interior space and a luggage boot space gets narrow. Such problem therefore arises in this case.
On the other hand, in the case of the battery pack structure disclosed in the Patent Document 2, such problem that the vehicle body floor upper space gets narrow due to the mounting of the high-power cut-off switch can be solved. However, since the high-power cut-off switch is provided with the high-power cut-off switch arranged parallel to the battery module in the vehicle width direction, in a case where a maximum width size of the battery case is previously determined, there is no other way than to narrow an area width size that is set as the battery module mounting area. As a consequence, there arises a problem of decreasing or narrowing a battery mounting space where the battery module can be mounted inside the battery case.